Anthem Statement M1 monoblock power amplifier

When I first saw Anthem Statement's M1 at the 2011 CEDIA Expo, it was a bolt from the blue. Happening on this flat, black slab of an amplifier lying on a display table or bolted to a wall, reminded me of the appearance of the iconic monolith in Stanley Kubrick and Arthur C. Clarke's 2001: A Space Odyssey. The M1's dimensional ratios are not 12:22:32, and there are many other one-rack-unit ampsyet, like the monolith on the moon, the M1 was in such striking contrast to everything else in its environment that it demanded attention and reflection.

I soon learned that the M1 is a 1000W or 2000W (into 8 or 4 ohms) monoblock amplifier that costs $3499 each, $6998/pair. Of course, Anthem flowered from the ashes of Sonic Frontiers and continues to produce high-quality amplifiers, although today their image (if not their substance) is associated more with home-theater components than with the (mostly) tubed high-end audio gear Sonic Frontiers made. Indeed, this is the first single-channel amplifier to bear the Anthem logoand it's class-D to boot.

Class-D amplifiers are to the High End what electric cars are to the auto industry. Everyone acknowledges the advantages of the technology in terms of efficiency and ecological benevolence, but so far, neither has captured the souls of aficionados who demand cutting-edge sound regardless of the cost, whether in dollars or degrees. Anthem claims that the M1 is on that cutting edge. First, the ratio of the M1's power output to its size and weight is remarkable, as are its claimed distortion and noise specs. Second, in addition to the well-known efficiency of class-D circuitry, the M1 has an internal heat-pipe cooling system that allows multiple M1s to be stacked without the need for fans or bristling arrays of heatsink fins. Third, in contrast to most other class-D amps, which are based on a handful of commercially available core circuits or already populated circuit boards, Anthem claims to have created the M1 entirely in-house.

The M1 has a bridge-mode configuration using MOSFET power transistors, which means that its output is balanced, isolated from ground, and has lower ripple because it effectively doubles the supply ripple frequency and halves its voltage. The M1's power supply operates at 0.4MHz (400kHz), which is, consequently, its native pulse frequency. That frequency is directly modulated by the analog signal with a theoretically infinite time resolution. The resulting pulse-density (not pulse-width) modulated output is claimed to achieve a practical time resolution of 4 nanoseconds (0.000000004s), which is more than an order of magnitude better than that of the DSD coding used on SACD.

Pizza Delivery!
The M1's appearance and heritage, and the prospect of nearly limitless power, made the wait for its delivery seem, as when one orders out for dinner, much longer than it was. Anthem was generous in sending me three M1s so that, during the course of my listening for this reviewwhich is essentially of the M1's performance with two-channel recordingsI could also enjoy some multichannel listening: the front left, center, and right channels would have identical amplification.

Each M1 arrived in what looked like an outsized pizza box 2' square and 6" thick, suitable for the very largest, deep-dish, meat-lovers' pies. Inside, the M1 sat in a nest of firm foam, and was accompanied by an operating manual, a pair of rack-mount handles, and two power cords. One cord is a three-pronged 20A/240V cable, the other a two-pronged 15A/120V cable, with a two-conductor IEC connection at the amp end. I used the latter; I have only 15A lines in my apartment.

The manual indicates that the M1's continuous high-power output depends on the power supply, but offers a single set of specs without regard for the AC input. Anthem says that the M1 has power-factor correction, which ensures that voltage and current drawn from the wall are in-phase. A load-monitoring system, based on "a digitally modeled time constant of the circuit interruptor," allows large current surges that aren't long enough to result in excessive heat. As a result, while the M1 can put out 2kW continuously into 4 ohms when fed by 240V mains, it can still put out 2kW for the duration of typical musical peaks when fed by a dedicated 120V 15A line, without causing circuit interruption. I asked Anthem how best to set up three M1s with my two 15A lines. Surprisingly, they suggested that I plug them all into one line, but that if I used only two M1s, to plug each into its own line. I ran the M1s both ways and could hear no differences.

Setup was uneventful. After plugging the interconnects into the XLR inputs and attaching the speaker cables, I left each M1's gain-attenuation switch at 0dB to match the gain of my other amps, and set the M1s' On mode to Auto so that the amps would turn themselves on when they sensed the presence of a signal. Auto mode worked flawlessly when the M1s were directly connected to my Meridian 861 Reference v6 digital surround controller, but was sometimes spuriously triggered when connected via the DSPeaker Anti-Mode 2.0 room correction unit (see "Music in the Round," November 2012), which suggests that the latter is not as impervious to line noise as the Meridian.

The M1's front panel has only a power button and two LEDs. The power LED illuminates during normal operation; the status LED signals codes that indicate different problems with power or temperature, but remains steadily illuminated during normal operation. Both LEDs glow blue, and were either on or off throughout my listening, as no problems arose. With the three M1s neatly stacked, their potential to provide three channels of 2000W each into 4 ohms seemed almost a boastthey're smaller and lighter than my regular class-A/B amps, which output 250300Wpc.

The Entrée
I first listened to the M1s through ADAM Audio's Classic Column MK3 speakers, which I reviewed in August 2012. That audition was short but very compelling. The M1s seemed to give greater rein to the Columns' already very lively dynamics, but also gave a bit more depth to the soundstage, a bit more presence to the low voice range, and noticeably more power to the very bottom of the bass. The effect was immediately appealing and encouraging, but all too soon the Columns had to be sent to John Atkinson to be measured, and then back to the distributor.

Having read this review and the Mark Levinson review above, I'm having my doubts about class-D. It's been around for a while (not sure, did 47's Gain Card first employ this?) and certainly has its benefits in getting a lot of power out of a small package. Ideal for subwoofers I think, but what about the rest of the system? Do you think this technology will further develop into something truly great, or will class A/AB rule the roost?

Also a minor typo: a price discrepancy: "costs $3499 each, $7498/pair" the specs section has what appears to be the correct price though.

Since when have you been concerned about the technical aspects of something in Stereophile? Isn't all about how it "sounds"? I'm quite sure there are other types of class D circuits other than what you have mentioned and yes DIYaudio is full of successful builders........oh but wait those are HOBBYISTS......oh the horror!

It is interesting to follow class D technology to see where its going. Wyred4sound kind of tried to kick it off, for the masses, but still a bit (niet). I was/is/are a t-amp fan, and had high hopes, but, alas, I'm back to class A/B and quite happy with it (very good progress in that area for the record). The more I learn about how class-D works the more I appreciate how hard it is to get it right. As we all know, great for subwoofer amps. You can dial up several kilowatts without a blink. Class-D with feedback seem to be the best. Seems a bit complicated for me.

Actually, leaving aside the burn-in question in general, which I find varies from insignifican to significant depending upon the gear, I do not always find it positive. Although it is normally the case, assuming noticeable burn-in, I have encountered several pieces that went from being engaging to too polite. I'm just sayin'....

I was not stating that my experience is that "burn in" is always positive but that the vast majority of reports say so. In fact, the general description of "burn in" is that the device seems to settle in to its ideal performance disposition and that it is unfair to judge it before then. If so, how does it know to stop?

That is one reason why I am convinced that the vast majority of these reports are due to observer adaptation. This is not to say that nothing ever changes nor that careful listening cannot reveal greater insights over time. I suspect that your observations are a combination of some small effects and good observation.

Well, experience can encompass an interaction via any of our senses but, yes, our ears are the primary interface. However, our conscious experience via our ears (or any other sense) is always filtered by brain mechanisms that are hard-wired and/or functions of experience and mood. While one cannot turn these off, a good listener should have a decent awareness of how they determine what we perceive.

Its true from what i can see from the measurements that this Class D amp is not ready for prime-time. I'm suprised Anthem would release such a product for they can easily duplicate the measurements in this review. The very poor SNR and high ultra-sonics at 400kHz is inexcusable from a company like Anthem as i own their D2v prepro which is an excellent product IMHO.

This is not the first review to find problems with the M-1 btw. For KR to place it on a No-Recommended list is a very big deal in my view.

Thank you kindly for your review of the Anthem M1 monoblocks. I have been looking at Class D amps for a tri-amplified system using the DEQX as a base for xover and dsp (not the digital preamp feature). I look to use the M1 for my bass drivers moving to tube for mid/trebile in 3 way amplification mode (3 sets of monoblock).

I respond to this review as I am looking at this Anthem product reviewed with near perfect technicial measurements. I have not seen any review with these less poor result.

Based on some of your measurements, I am now going to go audition a pair rather than purchase outright on a trial peroid. I appreciate your efforts in this review